U.S. patent application number 14/067689 was filed with the patent office on 2014-05-08 for configuration of interference measurement resources for enhanced downlink measurements and mu-mimo.
This patent application is currently assigned to Samsung Electronics Co., LTD.. The applicant listed for this patent is Samsung Electronics Co., LTD.. Invention is credited to Younsun Kim, Young-Han Nam, Boon Loong Ng, Krishna Sayana, Yan Xin.
Application Number | 20140126402 14/067689 |
Document ID | / |
Family ID | 50622289 |
Filed Date | 2014-05-08 |
United States Patent
Application |
20140126402 |
Kind Code |
A1 |
Nam; Young-Han ; et
al. |
May 8, 2014 |
CONFIGURATION OF INTERFERENCE MEASUREMENT RESOURCES FOR ENHANCED
DOWNLINK MEASUREMENTS AND MU-MIMO
Abstract
Apparatuses and methods for indicating and performing
interference measurements. A method for performing interference
measurements includes identifying a CSI-IM configuration for the UE
to perform interference measurement. The method includes
determining whether the CSI-IM configuration includes a subset of a
total number of frequency resources configured for CSI-IM in the
wireless communication system. The method includes measuring
interference based on the identified CSI-IM configuration.
Additionally, the method includes sending feedback based on the
measured interference. The method for performing interference
measurements may also include determining whether to perform
interference measurements based on all downlink subframes or only a
portion of the downlink subframes. Additionally, the method may
include performing interference measurement based on the subframe
determination.
Inventors: |
Nam; Young-Han; (Plano,
TX) ; Sayana; Krishna; (San Jose, CA) ; Ng;
Boon Loong; (Dallas, TX) ; Kim; Younsun;
(Seongnam-shi, KR) ; Xin; Yan; (Princeton,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., LTD. |
Suwon-si |
|
KR |
|
|
Assignee: |
Samsung Electronics Co.,
LTD.
Suwon-si
KR
|
Family ID: |
50622289 |
Appl. No.: |
14/067689 |
Filed: |
October 30, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61722021 |
Nov 2, 2012 |
|
|
|
61756911 |
Jan 25, 2013 |
|
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Current U.S.
Class: |
370/252 |
Current CPC
Class: |
H04B 7/0632 20130101;
H04L 5/0051 20130101; H04L 5/0092 20130101; H04L 5/0057 20130101;
H04B 7/0452 20130101; H04W 24/08 20130101; H04B 7/0413 20130101;
H04B 7/0626 20130101 |
Class at
Publication: |
370/252 |
International
Class: |
H04W 24/08 20060101
H04W024/08 |
Claims
1. A method for performing interference measurements by a user
equipment (UE) in a wireless communication system, the method
comprising: identifying a channel state information (CSI)
interference measurement (IM) configuration for the UE to perform
interference measurement; determining whether or not the CSI-IM
configuration includes a subset of a total number of frequency
resources configured for CSI-IM in the wireless communication
system; measuring interference based on the identified CSI-IM
configuration; and sending feedback based on the measured
interference.
2. The method of claim 1, wherein the subset of a total number of
frequency resources configured for CSI-IM corresponds to at least
one subband of downlink system bandwidth, the method further
comprising: determining whether to perform subband based
interference measurements based on a signal received from a base
station.
3. The method of claim 1, wherein whether the UE is to use the
subset of frequency resources or the total number of frequency
resources to perform interference measurement is included as part
of a CSI process definition.
4. The method of claim 1, wherein the CSI-IM configuration is a
first CSI-IM configuration for the UE to perform interference
measurement based on the total number of frequency resources
configured for CSI-IM and the feedback is a first CSI feedback, the
method further comprising: identifying a second CSI-IM
configuration for the UE to perform interference measurement based
on the subset of frequency resources configured for CSI-IM;
performing a second measurement of interference based on the subset
of frequency resources configured for CSI-IM; and sending a second
CSI feedback based on the second measurement of interference.
5. The method of claim 1 further comprising: determining whether to
perform interference measurements based on all downlink subframes
or only a portion of the downlink subframes to form a subframe
determination; and performing interference measurement based on the
subframe determination, wherein whether to perform interference
measurements based on all downlink subframes or only a portion of
the downlink subframes is included in a CSI process definition.
6. An apparatus of a user equipment (UE) capable of performing
interference measurements in a wireless communication system, the
apparatus comprising: a controller configured to identify a channel
state information (CSI) interference measurement (IM) configuration
for the UE to perform interference measurement, determine whether
or not the CSI-IM configuration includes a subset of a total number
of frequency resources configured for CSI-IM in the wireless
communication system, and measure interference based on the
identified CSI-IM configuration; and a transmitter configured to
send feedback based on the measured interference.
7. The apparatus of claim 6, wherein the subset of a total number
of frequency resources configured for CSI-IM corresponds to at
least one subband of downlink system bandwidth, and wherein the
controller is configured to determine whether to perform subband
based interference measurements based on a signal received from a
base station.
8. The apparatus of claim 6, wherein whether the UE is to use the
subset of frequency resources or the total number of frequency
resources to perform interference measurement is included as part
of a CSI process definition.
9. The apparatus of claim 6, wherein: the CSI-IM configuration is a
first CSI-IM configuration for the UE to perform interference
measurement based on the total number of frequency resources
configured for CSI-IM and the feedback is a first CSI feedback; the
controller is configured to identify a second CSI-IM configuration
for the UE to perform interference measurement based on the subset
of frequency resources configured for CSI-IM and perform a second
measurement of interference based on the subset of frequency
resources configured for CSI-IM; and the transmitter is configured
to send a second CSI feedback based on the second measurement of
interference.
10. The apparatus of claim 6, wherein the controller is configured
to determine whether to perform interference measurements based on
all downlink subframes or only a portion of the downlink subframes
to form a subframe determination, and perform interference
measurement based on the subframe determination, wherein whether to
perform interference measurements based on all downlink subframes
or only a portion of the downlink subframes is included in a CSI
process definition.
11. A method for signaling interference measurements to be made by
a user equipment (UE) in a wireless communication system, the
method comprising: sending a signal indicating a channel state
information (CSI) interference measurement (IM) configuration for
the UE to perform interference measurement, wherein the CSI-IM
configuration includes an indication of whether the UE is to use a
subset of a total number of frequency resources configured for
CSI-IM in the wireless communication system; and receiving feedback
based on measured interference associated with the CSI-IM
configuration.
12. The method of claim 11, wherein the subset of a total number of
frequency resources configured for CSI-IM corresponds to at least
one subband of downlink system bandwidth.
13. The method of claim 11, wherein whether the UE is to use the
subset of frequency resources or the total number of frequency
resources to perform interference measurement is included as part
of a CSI process definition.
14. The method of claim 11, wherein the CSI-IM configuration is a
first CSI-IM configuration for the UE to perform interference
measurement based on the total number of frequency resources
configured for CSI-IM and the feedback is a first CSI feedback, the
method further comprising: indicating a second CSI-IM configuration
for the UE to perform interference measurement based on the subset
of frequency resources configured for CSI-IM; and receiving second
CSI feedback based measured interference associated with the second
CSI-IM configuration.
15. The method of claim 11 further comprising: indicating whether
to perform interference measurements based on all downlink
subframes or only a portion of the downlink subframes; and
receiving feedback based on interference measurement associated
with the subframe indication, wherein whether to perform
interference measurements based on all downlink subframes or only a
portion of the downlink subframes is included in a CSI process
definition.
16. An apparatus for signaling interference measurements to be made
by a user equipment (UE) in a wireless communication system, the
apparatus comprising: a transmitter configured to send a signal
indicating a channel state information (CSI) interference
measurement (IM) configuration for the UE to perform interference
measurement, wherein the CSI-IM configuration includes an
indication of whether the UE is to use a subset of a total number
of frequency resources configured for CSI-IM in the wireless
communication system; and a receiver configured to receive feedback
based on measured interference associated with the CSI-IM
configuration.
17. The apparatus of claim 16, wherein the subset of a total number
of frequency resources configured for CSI-IM corresponds to at
least one subband of downlink system bandwidth.
18. The apparatus of claim 16, wherein whether the UE is to use the
subset of frequency resources or the total number of frequency
resources to perform interference measurement is included as part
of a CSI process definition.
19. The apparatus of claim 16, wherein: the CSI-IM configuration is
a first CSI-IM configuration for the UE to perform interference
measurement based on the total number of frequency resources
configured for CSI-IM and the feedback is a first CSI feedback; the
transmitter is configured to indicate a second CSI-IM configuration
for the UE to perform interference measurement based on the subset
of frequency resources configured for CSI-IM; and the receiver is
configured to receive second CSI feedback based measured
interference associated with the second CSI-IM configuration.
20. The apparatus of claim 16, wherein: the transmitter is
configured to indicate whether to perform interference measurements
based on all downlink subframes or only a portion of the downlink
subframes; and the receiver is configured to receive feedback based
on interference measurement associated with the subframe
indication, wherein whether to perform interference measurements
based on all downlink subframes or only a portion of the downlink
subframes is included in a CSI process definition.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY
[0001] The present application claims priority to U.S. Provisional
Patent Application Ser. No. 61/722,021, filed Nov. 2, 2012,
entitled "Configuration of Interference Measurement Resources for
Enhanced Downlink Measurements and MU-MIMO" and U.S. Provisional
Patent Application Ser. No. 61/756,911, filed Jan. 25, 2013,.
entitled "Interference Measurement for Advanced Wireless
Communication Systems". The contents of both of the
above-identified patent documents are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present application relates generally to interference
present on signals transmitted and received in a wireless
communication system and, more specifically, to configuration of
resources to perform interference measurements in a wireless
communication system.
BACKGROUND
[0003] In Release-10 specification of long term evolution (LTE)
wireless communication standard, the user equipment (UE) feedbacks
a channel quality indication (CQI) in addition to a precoding
matrix index (PMI) and rank indicator, which correspond to a
supported modulation and coding scheme (MCS) level that can be
supported reliably by the UE, with a certain target error
probability. The feedback designs in Release-10 are designed for
single-user multiple-input multiple-output (MIMO) communication
techniques.
[0004] Multi-user (MU) MIMO corresponds to a transmission scheme,
where a transmitter transmits data to two or more UEs using the
same time/frequency resource by relying on spatial separation of
the corresponding user's channels. With support of up to four
transmit (Tx) antennas, transmission scheme designs are typically
designed for MU-MIMO support for the case of two user MU-MIMO
transmissions with a single stream per each UE.
[0005] Accordingly, there is a need for improved communication
techniques and standards for supporting MU-MIMO.
SUMMARY
[0006] Embodiments of the present disclosure provide configuration
of interference measurement resources for enhanced downlink
measurements and MU-MIMO.
[0007] In one exemplary embodiment, a method for performing
interference measurements by a UE is provided. The method includes
identifying a CSI-IM configuration for the UE to perform
interference measurement. The method also includes determining
whether the CSI-IM configuration includes a subset of a total
number of frequency resources configured for CSI-IM in the wireless
communication system. The method includes measuring interference
based on the identified CSI-IM configuration. Additionally, the
method includes sending feedback based on the measured
interference. The method for performing interference measurements
may also include determining whether to perform interference
measurements based on all downlink subframes or only a portion of
the downlink subframes. Additionally, the method may include
performing interference measurement based on the subframe
determination.
[0008] In another exemplary embodiment, an apparatus in a UE
capable of performing interference measurements in a wireless
communication system is provided. The apparatus includes a
controller and a transmitter. The controller is configured to
identify a channel state information CSI-IM configuration for the
UE to perform interference measurement, determine whether the
CSI-IM configuration includes a subset of a total number of
frequency resources configured for CSI-IM in the wireless
communication system, and measure interference based on the
identified CSI-IM configuration. The transmitter is configured to
send feedback based on the measured interference.
[0009] In yet another exemplary embodiment, a method for signaling
interference measurements to be made by a UE in a wireless
communication system is provided. The method includes sending a
signal indicating a CSI-IM configuration for the UE to perform
interference measurement. The CSI-IM configuration includes an
indication of whether the UE is to use a subset of a total number
of frequency resources configured for CSI-IM in the wireless
communication system. Additionally, the method includes receiving
feedback based on measured interference associated with the CSI-IM
configuration.
[0010] In yet another exemplary embodiment, an apparatus for
signaling interference measurements to be made by a UE in a
wireless communication system is provided. The apparatus includes a
transmitter and a receiver. The transmitter is configured to send a
signal identifying a CSI-IM configuration for the UE to perform
interference measurement. The CSI-IM configuration includes an
indication of whether the UE is to use a subset of a total number
of frequency resources configured for CSI-IM in the wireless
communication system. The receiver is configured to receive
feedback based on measured interference associated with the CSI-IM
configuration.
[0011] Before undertaking the DETAILED DESCRIPTION below, it may be
advantageous to set forth definitions of certain words and phrases
used throughout this patent document: the terms "include" and
"comprise," as well as derivatives thereof, mean inclusion without
limitation; the term "or," is inclusive, meaning and/or; the
phrases "associated with" and "associated therewith," as well as
derivatives thereof, may mean to include, be included within,
interconnect with, contain, be contained within, connect to or
with, couple to or with, be communicable with, cooperate with,
interleave, juxtapose, be proximate to, be bound to or with, have,
have a property of, or the like; and the term "controller" means
any device, system or part thereof that controls at least one
operation, such a device may be implemented in hardware, firmware
or software, or some combination of at least two of the same. It
should be noted that the functionality associated with any
particular controller may be centralized or distributed, whether
locally or remotely. Definitions for certain words and phrases are
provided throughout this patent document, those of ordinary skill
in the art should understand that in many, if not most instances,
such definitions apply to prior, as well as future uses of such
defined words and phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals represent like parts:
[0013] FIG. 1 illustrates an exemplary wireless system which
transmits messages in accordance with an illustrative embodiment of
the present disclosure;
[0014] FIG. 2 illustrates a high-level diagram of an orthogonal
frequency division multiple access transmit path in accordance with
an illustrative embodiment of the present disclosure;
[0015] FIG. 3 illustrates a high-level diagram of an orthogonal
frequency division multiple access receive path in accordance with
an illustrative embodiment of the present disclosure;
[0016] FIG. 4 illustrates a block diagram of a node in a wireless
communication system that may be used to implement various
embodiments of the present disclosure;
[0017] FIG. 5 illustrates CSI-IM configurations in accordance with
the various embodiments of the present disclosure;
[0018] FIG. 6 illustrates configured CSI-IM resource elements in
resource blocks in accordance with various embodiments of the
present disclosure;
[0019] FIG. 7 illustrates a subframe configuration for CSI-IM
resources in accordance with various embodiments of the present
disclosure;
[0020] FIG. 8 illustrates a CSI-IM resource configuration with a
resource configuration in each subband of a system bandwidth in
accordance with various embodiments of the present disclosure;
[0021] FIG. 9 illustrates a CSI-IM resource configuration with a
specific resource restriction configuration in accordance with an
illustrative embodiment of the present disclosure;
[0022] FIG. 10 illustrates a CSI-IM resource configuration with no
resource restriction for a first CSI Process and a CSI-IM resource
configuration with resource restriction to subband for a second CSI
Process in accordance with an illustrative embodiment of the
present disclosure;
[0023] FIG. 11 illustrates MU-MIMO communication with a UE
allocated to Port 7 and a UE allocated to Port 8 in accordance with
an illustrative embodiment of the present disclosure; and
[0024] FIG. 12 illustrates subframe transmissions for interference
measurement in time-domain in accordance with various embodiments
of the present disclosure.
DETAILED DESCRIPTION
[0025] FIGS. 1 through 12, discussed below, and the various
embodiments used to describe the principles of the present
disclosure in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
disclosure. Those skilled in the art will understand that the
principles of the present disclosure may be implemented in any
suitably-arranged system or device.
[0026] FIGS. 1-3 below describe various embodiments implemented in
wireless communications systems and with the use of OFDM or OFDMA
communication techniques. The description of FIGS. 1-3 is not meant
to imply physical or architectural limitations to the manner in
which different embodiments may be implemented. Different
embodiments of the present disclosure may be implemented in any
suitably-arranged communications system.
[0027] FIG. 1 illustrates exemplary wireless system 100, which
transmits messages according to the principles of the present
disclosure. In the illustrated embodiment, wireless system 100
includes transmission points (e.g., an Evolved Node B (eNB), Node
B), such as base station (BS) 101, base station (BS) 102, base
station (BS) 103, and other similar base stations or relay stations
(not shown). Base station 101 is in communication with base station
102 and base station 103. Base station 101 is also in communication
with Internet 130 or a similar IP-based system (not shown).
[0028] Base station 102 provides wireless broadband access (via
base station 101) to Internet 130 to a first plurality of user
equipment (e.g., mobile phone, mobile station, subscriber station)
within coverage area 120 of base station 102. The first plurality
of user equipment includes user equipment 111, which may be located
in a small business (SB); user equipment 112, which may be located
in an enterprise (E); user equipment 113, which may be located in a
WiFi hotspot (HS); user equipment 114, which may be located in a
first residence (R); user equipment 115, which may be located in a
second residence (R); and user equipment 116, which may be a mobile
device (M), such as a cell phone, a wireless laptop, a wireless
PDA, or the like.
[0029] Base station 103 provides wireless broadband access (via
base station 101) to Internet 130 to a second plurality of user
equipment within coverage area 125 of base station 103. The second
plurality of user equipment includes user equipment 115 and user
equipment 116. In an exemplary embodiment, base stations 101-103
may communicate with each other and with user equipment 111-116
using OFDM or OFDMA techniques.
[0030] While only six user equipment are depicted in FIG. 1, it is
understood that wireless system 100 may provide wireless broadband
access to additional user equipment. It is noted that user
equipment 115 and user equipment 116 are located on the edges of
both coverage area 120 and coverage area 125. User equipment 115
and user equipment 116 each communicate with both base station 102
and base station 103 and may be said to be operating in handoff
mode, as known to those of skill in the art.
[0031] User equipment 111-116 may access voice, data, video, video
conferencing, and/or other broadband services via Internet 130. In
an exemplary embodiment, one or more of user equipment 111-116 may
be associated with an access point (AP) of a WiFi WLAN. User
equipment 116 may be any of a number of mobile devices, including a
wireless-enabled laptop computer, personal data assistant,
notebook, handheld device, or other wireless-enabled device. User
equipment 114 and 115 may be, for example, a wireless-enabled
personal computer (PC), a laptop computer, a gateway, or another
device.
[0032] FIG. 2 is a high-level diagram of transmit path circuitry
200. For example, the transmit path circuitry 200 may be used for
an orthogonal frequency division multiple access (OFDMA)
communication. FIG. 3 is a high-level diagram of receive path
circuitry 300. For example, the receive path circuitry 300 may be
used for an orthogonal frequency division multiple access (OFDMA)
communication. In FIGS. 2 and 3, for downlink communication, the
transmit path circuitry 200 may be implemented in base station (BS)
102 or a relay station, and the receive path circuitry 300 may be
implemented in a user equipment (e.g. user equipment 116 of FIG.
1). In other examples, for uplink communication, the receive path
circuitry 300 may be implemented in a base station (e.g. base
station 102 of FIG. 1) or a relay station, and the transmit path
circuitry 200 may be implemented in a user equipment (e.g. user
equipment 116 of FIG. 1).
[0033] Transmit path circuitry 200 comprises channel coding and
modulation block 205, serial-to-parallel (S-to-P) block 210, Size N
Inverse Fast Fourier Transform (IFFT) block 215, parallel-to-serial
(P-to-S) block 220, add cyclic prefix block 225, and up-converter
(UC) 230. Receive path circuitry 300 comprises down-converter (DC)
255, remove cyclic prefix block 260, serial-to-parallel (S-to-P)
block 265, Size N Fast Fourier Transform (FFT) block 270,
parallel-to-serial (P-to-S) block 275, and channel decoding and
demodulation block 280.
[0034] At least some of the components in FIGS. 2 and 3 may be
implemented in software, while other components may be implemented
by configurable hardware or a mixture of software and configurable
hardware. In particular, it is noted that the FFT blocks and the
IFFT blocks described in this disclosure document may be
implemented as configurable software algorithms, where the value of
Size N may be modified according to the implementation.
[0035] Furthermore, although this disclosure is directed to an
embodiment that implements the Fast Fourier Transform and the
Inverse Fast Fourier Transform, this is by way of illustration only
and should not be construed to limit the scope of the disclosure.
It will be appreciated that in an alternate embodiment of the
disclosure, the Fast Fourier Transform functions and the Inverse
Fast Fourier Transform functions may easily be replaced by Discrete
Fourier Transform (DFT) functions and Inverse Discrete Fourier
Transform (IDFT) functions, respectively. It will be appreciated
that for DFT and IDFT functions, the value of the N variable may be
any integer number (i.e., 1, 2, 3, 4, etc.); while for FFT and IFFT
functions, the value of the N variable may be any integer number
that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).
[0036] In transmit path circuitry 200, channel coding and
modulation block 205 receives a set of information bits, applies
coding (e.g., LDPC coding) and modulates (e.g., Quadrature Phase
Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM)) the
input bits to produce a sequence of frequency-domain modulation
symbols. Serial-to-parallel block 210 converts (i.e.,
de-multiplexes) the serial modulated symbols to parallel data to
produce N parallel symbol streams where N is the IFFT/FFT size used
in BS 102 and UE 116. Size N IFFT block 215 then performs an IFFT
operation on the N parallel symbol streams to produce time-domain
output signals. Parallel-to-serial block 220 converts (i.e.,
multiplexes) the parallel time-domain output symbols from Size N
IFFT block 215 to produce a serial time-domain signal. Add cyclic
prefix block 225 then inserts a cyclic prefix to the time-domain
signal. Finally, up-converter 230 modulates (i.e., up-converts) the
output of add cyclic prefix block 225 to RF frequency for
transmission via a wireless channel. The signal may also be
filtered at baseband before conversion to RF frequency.
[0037] The transmitted RF signal arrives at UE 116 after passing
through the wireless channel, and reverse operations to those at BS
102 are performed. Down-converter 255 down-converts the received
signal to baseband frequency, and remove cyclic prefix block 260
removes the cyclic prefix to produce the serial time-domain
baseband signal. Serial-to-parallel block 265 converts the
time-domain baseband signal to parallel time-domain signals. Size N
FFT block 270 then performs an FFT algorithm to produce N parallel
frequency-domain signals. Parallel-to-serial block 275 converts the
parallel frequency-domain signals to a sequence of modulated data
symbols. Channel decoding and demodulation block 280 demodulates
and then decodes the modulated symbols to recover the original
input data stream.
[0038] Each of base stations 101-103 may implement a transmit path
that is analogous to transmitting in the downlink to user equipment
111-116 and may implement a receive path that is analogous to
receiving in the uplink from user equipment 111-116. Similarly,
each one of user equipment 111-116 may implement a transmit path
corresponding to the architecture for transmitting in the uplink to
base stations 101-103 and may implement a receive path
corresponding to the architecture for receiving in the downlink
from base stations 101-103.
[0039] FIG. 4 illustrates a block diagram of a node 400 in a
wireless communication system that may be used to implement various
embodiments of the present disclosure. In this illustrative
example, the node 400 is a device at a communication point in a
wireless communications system, such as, for example, wireless
system 100 in FIG. 1. The node 400 may be a base station (e.g.,
eNB, RS, RRH, etc.) or a user equipment (e.g., mobile station,
subscriber station, etc.). In one example, the node 400 is an
example of one embodiment of the user equipment 116 in FIG. 1. In
another example, the node 400 is an example of one embodiment of
the base station 102 in FIG. 1. Node 400 comprises transmit (TX)
antennas 405, transmit (TX) processing circuitry 410, receive (Rx)
antennas 415, receive (Rx) processing circuitry 420, and controller
425.
[0040] TX processing circuitry 410 receives analog or digital
signals from outgoing baseband data. TX processing circuitry 410
encodes, multiplexes, and/or digitizes the outgoing baseband data
to produce a processed RF signal that is transmitted via TX
antennas 405. For example, the TX processing circuitry 410 may
implement a transmit path that is analogous to the transmit
processing circuitry 200 in FIG. 2. TX processing circuitry 410 may
also perform spatial multiplexing via layer mapping to different
antennas in TX antennas 405 and different ports of antennas in TX
antennas 405.
[0041] Rx processing circuitry 420 receives from Rx antennas 415 an
incoming RF signal or signals transmitted by one or more
transmission points, such as base stations, relay stations, remote
radio heads, user equipment, etc. Rx processing circuitry 420
processes the received signal(s) to identify the information
transmitted by the transmission point(s). For example, the Rx
processing circuitry 420 may down-convert the incoming RF signal(s)
to produce an intermediate frequency (IF) or a baseband signal by
channel estimation, demodulating, stream separating, filtering,
decoding, and/or digitizing the received signal(s). For example,
the Rx processing circuitry 420 may implement a receive path that
is analogous to the receive processing circuitry 300 in FIG. 3.
[0042] Controller 425 controls the overall operation of node 400.
In one such operation, controller 425 controls the reception of
channel signals and the transmission of channel signals by Rx
processing circuitry 420 and TX processing circuitry 410, in
accordance with well-known principles.
[0043] The embodiment of node 400 illustrated in FIG. 4 is for
illustration only. Other embodiments of the node 400 could be used
without departing from the scope of this disclosure. For example,
the antennas in the TX and Rx antenna arrays may overlap or be the
same antenna arrays used for transmission and reception via one or
more antenna switching mechanisms.
[0044] A channel state information (CSI) reference signal (RS)
enables channel measurements by a UE. A UE specific CSI-RS
configuration includes: 1) a non-zero power (NZP) CSI-RS resource;
and 2) one or more zero-power CSI-RS resources. Typically, the
non-zero power CSI-RS resource corresponds to the antenna
elements/ports of the serving cell. Zero-power (ZP) CSI-RS, also
commonly referred to as muted CSI-RS, are used to protect the
CSI-RS resources of another cell, and a UE is expected to rate
match (skip for decoding/demodulation) around these resources. The
following standards documents are incorporated by reference herein:
1) 3GPP TS 36.211 v10.1.0, "E-UTRA, Physical channels and
modulation;" 2) 3GPP TS 36.212 v10.1.0, "E-UTRA, Multiplexing and
Channel coding;" 3) 3GPP TS 36.213 v10.1.0, "E-UTRA, Physical Layer
Procedures;" 4) RP-111365 Coordinated Multi-Point Operation for LIE
WID; 5) 3GPP TS 36.819 V11.0.0 (2011-09); 6) 3GPP TS 36.331 draft
version RP-121970; 7) 3GPP 36.213 v11.1.0; and 8) 3GPP TS 36.331
draft version RP-121970.
[0045] Additional configuration details of the CSI-RS are specified
in 3GPP standards, particularly in 36.211 section 6.10.5 and 36.213
section 7.2.5. A draft version of 36.331 (RP-121970) provides
additional configuration details of the NZP CSI-RS configuration.
3GPP 36.213 v11.1.0 describes additional details of CSI-IM resource
configuration, particularly in sections 7.2, 7.2.3, &
7.2.6.
[0046] In U.S. patent application Ser. No. 13/888,659 entitled "CSI
DEFINITIONS AND FEEDBACK MODES FOR COORDINATED MULTI-POINT
TRANSMISSION" filed May 9, 2012, which is incorporated by reference
herein, the interference measurement procedure captured in Section
7.2.3 of 36.211 is described where IMR refers to CSI-IM resource.
In one method, with IMR resource configuration, the reference
subframe is based on the intersection of the IMR resource and the
CSI subframe subset. This may be achieved by modifying the
definition of a valid downlink subframe, for example, as
illustrated in FIGS. 9A and 9B of application Ser. No.
13/888,659.
[0047] Additional details of CSI-IM are described in a draft
version of 36.331 (RP-121970). Additional details regarding the RI
reference process are provided in 36.213 v11.1.0, particularly in
sections 7.2.1 and 7.2.2. Additional details regarding CSI
reference resources are provided in 36.213 v11.1.0, particularly in
section 7.2.3.
[0048] To support coordinated multipoint (CoMP) transmission, a
network uses feedback corresponding to multiple transmission points
or cells. As a result, a network may set up multiple CSI-RS
resources, each typically corresponding to a transmission point
(TP) or CSI process. Unless otherwise stated, the terms "CSI-RS
resource," "TP," and "CSI process" may be used interchangeably.
Further details of CSI-RS resource configurations and the
configurable parameters for each CSI-RS resource may include
configuration of multiple non-zero power CSI-RS resources and
include at least: AntennaPortsCount, ResourceConfig,
SubframeConfig, P.sub.c, and a Parameter X to derive scrambling
initialization
c.sub.init=2.sup.10(7(n.sub.s+1)+l+1)(2X+1)+2X+N.sub.CP. X ranges
from 0 to 503 and may be interpreted as virtual cell id. In Release
10, X is the PCI of the serving cell. These parameters are
configured per CSI-RS resource. Some parameters may be configured
per CSI-RS port considering the decision of supporting coherent
joint transmission by the aggregate CSI feedback corresponding to
multiple TPs in one CSI-RS resource. While the CSI-RS resources
capture channels of individual TPs, the interference measurement
also depends on the CoMP scheme. In Releases 8-10, a single
interference measurement resource is used, which is the
cell-specific reference signal (CRS) itself. Interference
measurement on CRS captures all the interference outside the
cell.
[0049] For CoMP, one or more interference measurement resources may
be defined to capture the interference for a hypothetical CoMP
scheme. At least one Interference Measurement Resource (IMR) (also
referred to as a CSI-interference measurement (IM) resource or
CSI-IM resource) may be configured for a Release-11 UE. A maximum
of only one or multiple IMRs may be configured for a Release-11 UE.
Each IMR may consist of only REs, which may be configured as
Release 10 CSI-RS resources.
[0050] For IMR configuration, each IMR may be configured
independently with a Release-10 subframeConfig and a Release-10
resourceConfig, where resourceConfig is for 4 REs. All the IMRs
configured for one UE may together use only REs which may be
configured as a single R10 ZP CSI-RS resource configuration. To be
consistent with the terminology used by the specification, the
present disclosure refers to the IMR resources as CSI-IM resources
(i.e., CSI resources for interference measurement).
[0051] Embodiments of the present disclosure provide various
methods to use the defined CSI-IM resources to capture co-channel
interference, multi user interference, and/or frequency selective
interference. These CSI-IM resources were originally designed for
capturing different hypothesis of inter-TP/inter-cell interference
that is used for reporting CSI to aid the CoMP scheduling
decisions. In wireless networks, the network utilizes the UEs' CSI
to schedule time-frequency resources and to select precoders and
MCSs for each individual UE. To facilitate the UEs' CSI estimation,
the network may configure and transmit CSI reference signals (RS)
as described above. At the same time, each UE may be configured to
feedback estimated precoding matrix information (PMI), channel
quality information (CQI) and rank information (RI), by receiving
and processing the CSI-RS. Further, in Release-11, a new type of
reference resources, namely CSI-IM resources, are introduced for
interference measurements. With one or more interference
measurement resources (e.g., CSI-IM) supported for CoMP, CSI
measurement is based on both a CSI-RS resource and a CSI-IM
resource. Hence, to set up feedback, a CSI process is defined. Each
CSI process is defined with an associated (CSI-RS resource, CSI-IM
resource) pair.
[0052] Embodiments of the present disclosure recognize that with
MU-MIMO, the MCS to be used by the scheduler for each user needs to
be determined at the eNB; the MCS that may be supported reliably
for each UE is dependent on co-channel PMI corresponding to the
co-scheduled UE; and that, on the other hand, for scheduling
flexibility, a transmitter may pair a UE with any other UE.
Accordingly, embodiments of the present disclosure provide methods
to compute MU-CQI at the UE. As such, the reported MU-CQI allows
better prediction at the eNB. Embodiments of the present disclosure
recognize that relying completely on eNB predictions of MCS may not
be accurate, since the receiver implementation specific algorithms,
such as interference cancellation/suppression, also need to be
accurately reflected in any MU-CQI calculation.
[0053] Embodiments of the present disclosure recognize that the
CSI-IM are transmitted in a time and frequency pattern and
represent interference that may be flat over time and frequency.
For example, the network reflects interference from one or more
transmission points/sites in the system. It is left to the UE
implementation to determine how the interference is averaged over
the subframes and subbands. Accordingly, embodiments of the present
disclosure provide methods to reuse CSI-IM resources to achieve UE
interference measurements for MU-CQI purposes.
[0054] FIG. 5 illustrates CSI-IM configurations in accordance with
the various embodiments of the present disclosure. CSI-IM Config 1
505 illustrates multiple configured CSI-IM resources across
multiple subbands representing the entire frequency band. The UE
may utilize the multiple CSI-IM resources configured across
multiple subbands to perform wideband (WB) co-channel interference
measurements. CSI-IM Config 2 510 illustrates configured CSI-IM
resources in various subband sets across the entire frequency band.
In various embodiments, the UE is configured (e.g., by the eNB) for
interference measurement using a set of the total configured CSI-IM
resources across the entire frequency band. For example, the UE may
only use frequency resources present in one or more subbands to
perform subband (SB) co-channel interference measurements.
[0055] FIG. 6 illustrates configured CSI-IM resource elements in
resource blocks in accordance with various embodiments of the
present disclosure. A CSI-IM resource configuration as defined in
Release-11 spans the entire frequency band and occurs periodically
in certain subframes. It is left to the UE implementation to
determine how to average the interference measurements based on the
CSI-IM resources. For example, when CSI-RS resource configuration 0
is configured, the UE is configured with each of the shaded CSI-IM
resources illustrated in FIG. 6 across the downlink system
bandwidth. In this illustrative example, four REs are present in
each RB for configuration 0. Other configurations have the same
density of resources per RB but with different locations (i.e.,
resource configuration) within the RB grid.
[0056] FIG. 7 illustrates a subframe configuration 700 for CSI-IM
resources in accordance with various embodiments of the present
disclosure. In this illustrative embodiment, a subframe
configuration (i.e., additional subframe timing associated with
IMRs) is illustrated, which corresponds to the subframe period of
5ms and the subframe offset of 1 ms.
[0057] In various embodiments of the present disclosure, a resource
configuration (e.g., a restriction on the total number of
configured resources) is defined in frequency for measurements
based on CSI-IM. The resource configuration corresponds to a set of
valid frequency resources over which the CSI-IM resources may be
used by the UE to perform interference measurements. In an
illustrative example, information of the set one or more valid
frequency locations is included as part of a CSI process
configuration. Such one or more frequency locations determine the
locations where CSI-IM resources may be used for the purpose of CSI
derivation.
[0058] For example, as illustrated in FIG. 6, the CSI-IM resource
configuration for the UE may be those CSI-IM resources located in
the RBs labeled as valid resources for interference measurement. In
one exemplary embodiment, the information related to one or more
frequency locations is the set of subbands where the CSI-IM
resource must be derived from for CSI measurement. Supported
subband sizes (k) based on the system bandwidth are provided in
Table 7.2.1-3 of 36.213 v 10.0. Resource restriction in frequency
for measurements may provide many benefits. A key reason is when
the network anticipates the heavier load in certain bands compared
to others due to deployment of certain devices (e.g., deployment of
MTC devices in the center 6 RBs or fixed assignments of ePDCCH
search space for a set of UEs) in these bands or due to fixed or
persistent assignments of certain physical channels in certain
locations.
[0059] In various embodiments of the present disclosure, the
information related to one or more frequency locations is signaled
as part of downlink control information (DCI) configuration. In one
embodiment, the downlink control information (DCI) may be used to
signal a selection between one or more configurations, each of
which correspond information related to one or more frequency
locations. Exemplary DCI signaling CSI-IM resource configuration
indications are illustrated in Table 1.
TABLE-US-00001 TABLE 1 DCI bit-field value CSI-IM Resource
Configuration 0 First set of frequency locations of a CSI-IM
configuration configured by higher layers 1 Second set of frequency
locations of a CSI-IM configuration configured by higher layers
[0060] In one embodiment, the DCI format used may be DCI format 0
or 4 or a similar DCI format which includes an uplink grant and is
used to trigger an associated aperiodic CSI feedback on the uplink.
An aperiodic CSI feedback may be associated with feedback of one or
more CSI processes. In such a case, the DCI bit-field may indicate
resource restrictions per CSI process or a single resource
restriction for all CSI processes.
[0061] In various embodiments of the present disclosure, for
feedback modes that include subband feedback (e.g., feedback of
subband CQI), the UE measures the interference measurements based
on the corresponding subband on which a subband CQI is reported.
The PUSCH and PUCCH based feedback modes supported in Release-10
LTE are described in Tables 7.2.1-1 and 7.2.2-1 of 36.213 v
10.0.
[0062] The CSI reference resource is defined as follows in the
frequency domain. The CSI reference resource is defined by the
group of downlink physical resource blocks corresponding to the
band to which the derived CQI value relates. However, the
interference measurements at the UE may assume that the
interference behavior on CSI-IM resources is statistically similar
across the whole bandwidth as opposed to the channel measurements.
In one example, whether to perform subband-based interference
measurements or not is specifically signaled by an eNB. Such
signaling may be higher layer configured or dynamically signaled
using a DCI format. In another example, the dynamic signaling of
such information is included as part of the aperiodic CSI request
in a downlink DCI format (e.g., DCI Format 0 or Format 4).
[0063] In various embodiments of the present disclosure, the signal
model with MU transmission may be expressed according to Equation 1
below with two transmit antennas and two receive antennas:
Y 1 = H 1 V 1 s 1 + H 1 G 1 s 2 + n 1 = [ h 11 h 21 h 12 h 22 ] [ v
11 v 12 ] s 1 + [ h 11 h 21 h 12 h 22 ] [ q 21 g 22 ] s 2 + n 1
Equation 1 ##EQU00001##
where Y.sub.1 is the received signal at UE1, H.sub.1 is the
2.times.2 MIMO channel matrix at UE1, V.sub.1 is the precoder
applied for UE1 data symbol s.sub.1, G.sub.1 is the precoder
applied for interfering UE2 data symbol s.sub.2, and n.sub.1 is the
observed AWGN noise at the receiver.
[0064] More generally, the signal model may be expressed according
to Equation 2 below:
Y.sub.1=H.sub.1V.sub.1s.sub.1+H.sub.1G.sub.I{right arrow over
(s)}.sub.I+n.sub.1 Equation 2
where G.sub.I=[G.sub.1, G.sub.2, . . . G.sub.N.sub.I] is the
precoding vector corresponding to data symbols that are transmitted
to other users s.sub.I=[s.sub.1, s.sub.2, . . . s.sub.N.sub.I].
[0065] The most accurate estimate of MU-CQI may be achieved if the
transmitter (eNB) and receiver (UE) are aligned on the assumption
of co-channel PMI G.sub.I. However, with multi-user scheme support
at the eNB, a scheduler determines the user grouping for MU
transmission based on the channel state feedback received from all
UEs, the data requirements of each user, and other fairness
metrics. A UE receiver may not exactly predict the co-channel PMI
used for MU transmission and, hence, it may not be feasible to
exactly account for the co-channel PMI used in the CQI calculation.
In one example, one possibility is for the eNB to explicitly
indicate such precoder ahead of time for MU-CQI calculation. This
method may have some disadvantages. Due to the limitation on amount
of signaling overhead that may be supported on the downlink,
co-channel PMI may not be able to be indicated often or in a
frequency-selective manner. In one embodiment, the co-channel
interference is indicated implicitly using CSI-IM resources.
[0066] FIG. 8 illustrates a CSI-IM resource configuration 800 with
a resource configuration in each subband of a system bandwidth in
accordance with various embodiments of the present disclosure. In
this illustrative embodiment, a CSI feedback is based on a CSI
process and CSI-IM measurements configured for or restricted to the
corresponding subband or subbands in the frequency. The
"corresponding subband" is the set of subbands that the CQI
feedback relates to in the feedback mode. In one embodiment,
whether such configuration or restriction applies is signaled by a
higher layer parameter. In one embodiment, this configuration is
indicated and/or included as part of the CSI process definition as
illustrated in Table 2 below.
TABLE-US-00002 TABLE 2 CSI-Process: { CSI-Process-ID Integer
CSI-RS-config CSI-IM-config (Optional) Flag_Subband_CSI-IM
measurement Boolean }
[0067] In one embodiment, the CSI feedback corresponding to such
CSI process is reported with a rank configuration or restriction.
In one method, the rank of the CSI feedback is configuration or
restricted to rank 1. In another example, the rank of such CSI
process may be higher layer configured. In another example, whether
such a configuration or restriction applies is indicated as part of
a periodic or aperiodic feedback mode configuration.
[0068] In an exemplary embodiment, as illustrated, for example, in
FIG. 5, a first CSI feedback is based on a first CSI process and no
resource restriction in frequency (e.g., CSI-IM Config 1 505). A
second CSI feedback is based on a second CSI process and CSI-IM
measurements configured for or restricted to a corresponding
subband in frequency (e.g., CSI-IM Config 2 510). The first CSI
feedback is reported along with the reported rank (RI) chosen by
the UE. The second CSI feedback is reported with a rank
configuration or restriction. In one example, the rank of the
second CSI feedback is configured or restricted to rank 1. In
another example, the rank of the second process is higher layer
configured. In another example, the rank of the second process may
be dependent on the rank of the first process. In one example of
this embodiment, the second CSI feedback and the first CSI feedback
may be sent with the same rank (e.g., rank 1).
[0069] In one embodiment, a common PMI is configured between the
first and second CSI process (i.e., the second CSI process does not
report PMI feedback). In one example, the second CSI process
reports the CQI as a delta CQI to the first CSI process. In another
example, the first and second CSI processes are reported together
(configured together) for an aperiodic CSI feedback mode. In
particular, these methods may be used for PUSCH based 3-2 aperiodic
feedback mode. It may be difficult to justify PUSCH 3-2 feedback
payload without corresponding gains, so a second CSI process may
measure MU-CQI. The eNB may obtain accurate CQI using any
particular form of precoding (e.g., ZF precoding) since the effect
of precoding may be reflected on CSI-IM resources.
[0070] In one example, the above embodiments corresponding to two
different CSI reports may be implemented as a single joint CSI
process to support dynamic MU as illustrated in Table 3 below. In
this example, an eNB may reflect co-channel interference on the
CSI-IM measurement.
TABLE-US-00003 TABLE 3 CSI-Process-MU: { CSI-Process-ID Integer
CSI-RS-config CSI-IM-config1 CSI-IM-config2 (Optional) MU_flag
Boolean (Optional) Flag_Subband_CSI-IM-config2 Boolean (Optional)
Rank_restriction_MU }
[0071] With this configuration, a first CSI feedback is based on
the single (NZP) CSI-RS configuration and CSI-IM config 1. A second
CSI feedback suitable for MU is reported based on the single CSI-RS
configuration and CSI-IM config 2 with the subband restriction as
indicated by the Flag_Subband_CSI-IM-config2. Further, rank
restriction is configured by Rank_restriction_MU.
[0072] FIG. 9 illustrates a CSI-IM resource configuration 900 with
a specific resource restriction configuration in accordance with an
illustrative embodiment of the present disclosure. In this
illustrative embodiment, a CSI feedback is based on a CSI process
and CSI-IM measurements restricted to a configured set of subbands
in frequency, referred to as a resource restriction configuration.
In one example, resource restriction configuration is signaled by a
higher layer parameter. In one example, this resource restriction
configuration is included as part of the CSI process definition as
illustrated in Table 4 below.
TABLE-US-00004 TABLE 4 CSI-Process: { CSI-Process-ID Integer
CSI-RS-config CSI-IM-config (Optional)
Reseource_Restriction_configuration_CSI-IM Bitmap measurement }
[0073] FIG. 10 illustrates a CSI-IM resource configuration 1005
with no resource restriction for a first CSI Process, and a CSI-IM
resource configuration 1010 with resource restriction to subband
for a second CSI Process in accordance with an illustrative
embodiment of the present disclosure. In this illustrative
embodiment, a first CSI feedback is based on a first CSI process
and no resource restriction in frequency. A second CSI feedback is
based on a second CSI process and CSI-IM measurements restricted to
a restricted set of frequency locations (illustrated as resource
restriction (RR) configuration). In one example, the restricted set
of frequency locations is a set of subbands. The first CSI feedback
is reported along with the reported rank (RI) chosen by the UE. The
second CSI feedback is reported with a rank restriction. In one
method, the rank of the second CSI feedback is restricted to rank
1. In another example, the rank of the second process is higher
layer configured. In another example, the rank of the second
process is dependent on the rank of the first process.
[0074] In one example of this embodiment, the second CSI feedback
and the first CSI feedback are sent with the same rank (e.g., rank
1). In another example, a common PMI is configured between the
first and second CSI processes, i.e., the second CSI process does
not report PMI feedback. In one method, the second CSI process
reports the CQI as a delta CQI to the first CSI process. In
particular, these examples may be used for PUSCH aperiodic feedback
modes, both subband based and wideband based modes. The eNB may
obtain accurate CQI using any particular form of precoding (e.g.,
ZF precoding), since the effect of precoding may be reflected on
CSI-IM resources.
[0075] In one example, the above embodiments corresponding to two
different CSI reports are implemented as two separate CSI processes
to support dynamic MU as illustrated in Tables 5 and 6 below. In
this example, an eNB may reflect co-channel interference on the
CSI-IM measurement.
TABLE-US-00005 TABLE 5 CSI-Process1: { CSI-Process-ID Integer
CSI-RS-config CSI-IM-config1 (Optional) MU_flag Boolean (Optional)
Resource_Restriction_configuration_CSI-IM Bitmap measurement
(Optional) Rank_restriction_MU }
TABLE-US-00006 TABLE 6 CSI-Process2: { CSI-Process-ID Integer
CSI-RS-config CSI-IM-config2 (Optional) MU_flag Boolean (Optional)
Resource_Restriction_configuration_CSI-IM Bitmap measurement
(Optional) Rank_restriction_MU }
[0076] With this configuration, a first CSI feedback is based on
the single (NZP) CSI-RS configuration and CSI-IM config 1. A second
CSI feedback suitable for MU is reported based on the single CSI-RS
configuration and CSI-IM config 2 with the resource restriction for
interference measurement as indicated by the
Resource_Restriction_configuration_CSI-IM measurement. Further rank
restriction is as configured by Rank_restriction_MU.
[0077] In various embodiments of the present disclosure, the UE
measures the MU interference assuming no receiver processing. In
practice, the pilots/reference symbols (RS) corresponding to an
interfering UE may be available to a user. An advanced UE receiver
may detect and cancel such interference. For example, the signal
model after receive processing may be expressed according to
Equation 3 below:
{right arrow over (w)}Y.sub.1={right arrow over
(w)}H.sub.1V.sub.1s.sub.1+{right arrow over
(w)}H.sub.1G.sub.I{right arrow over (s)}.sub.I+{right arrow over
(w)}n.sub.1 Equation 3
where {right arrow over (w)} are computed based on the channels
H.sub.1V.sub.1 and H.sub.1G.sub.I.
[0078] FIG. 11 illustrates MU-MIMO communication with a UE 1105
allocated to Port 7 and a UE 1110 allocated to Port 8 in accordance
with an illustrative embodiment of the present disclosure. In
actual MU receiver processing, the channel of an interfering MU-UE
may be estimated by the UE on the DRMS port that is allocated to an
interfering UE. In this illustrative example, a DMRS port 7 is
assigned to the UE 1105, and the DMRS port 8 is assigned to an
interfering UE 1110.
[0079] The present disclosure provides several exemplary
implementations to reflect this receiver behavior for accurate
MU-CQI estimation. In one example, a CSI feedback is based on, i) a
first type non-zero power CSI-RS for channel measurements, ii)
second type non-zero power CSI-RS for MU interference measurements,
and iii) a CSI-IM for interference measurements. For CSI
computation at the UE, the UE treats the first non-zero power
CSI-RS as the unprecoded channel for channel measurements. The
second non-zero power CSI-RS is treated as a precoded interfering
channel (H.sub.1G.sub.I) for interference measurements associated
with a corresponding DMRS port in a hypothetical PDSCH resource.
The CSI-IM is simply treated as an interference that is seen on
each hypothetical PDSCH for a UE.
[0080] In one embodiment, CSI process definition is modified as
follows to include information of the DMRS ports of the self and
interfering channels as illustrated in Table 7 below.
TABLE-US-00007 TABLE 7 (MU) CSI process definition 1 { Non-zero
CSI-RS resource configuration of first type; Non-zero CSI-RS
resource configuration of a second type; A CSI-IM configuration;
(optional) A DMRS port associated with the non-zero CSI-RS resource
configuration of first type; (optional) A DMRS port associated with
the non-zero CSI-RS resource configuration of second type; }
[0081] In one embodiment, CSI process definition includes
information on whether the DMRS ports of the self and interfering
channels collide or not, as illustrated in Table 8 below. In one
example, ports 7 and 8 occupy the same set of time and frequency
resources while being separated by CDM. In another example, ports 7
and 8 occupy different sets of time and frequency resources.
TABLE-US-00008 TABLE 8 (MU) CSI process definition 2 { Non-zero
CSI-RS resource configuration of first type; Non-zero CSI-RS
resource configuration of a second type; A CSI-IM configuration;
(optional) A bit field indicating whether the DMRS port
corresponding to non-zero CSI-RS resource configuration of the
second type is colliding with the DMRS port corresponding to
non-zero CSI-RS resource configuration of first type }
[0082] In one exemplary embodiment, a separate value of Pc is
indicated for the non-zero CSI-RS configuration of a second
type.
[0083] The PUSCH and PUCCH based feedback modes supported in the
legacy LTE are described in 36.213 v.10.0.0 and, in particular, in
Tables 7.2.1-1 and 7.2.2-1. In Table 7.2.1-1, a new PUSCH CQI
feedback mode, mode 3-2, is provided for configuring CSI feedback
of higher-layer configured subband CQI and multiple PMI.
[0084] In various embodiments, for feedback modes that include
subband feedback (e.g., feedback of subband CQI, i.e., PUSCH mode
2-0, 2-2, 3-0, 3-1 and 3-2; and PUCCH mode 2-0 and 2-1), the UE
measures the interference measurements based on the corresponding
subband on which a subband CQI is reported. Currently, the CSI
reference resource is defined as follows in 36.213.
[0085] Various embodiments of the present disclosure recognize
that, for the interference measurements at a UE, the UE may assume
that the interference behavior on CSI-IM resources is statistically
similar across the whole bandwidth, as opposed to the channel
measurements. Various embodiments of the present disclosure
recognize also that subband-restricted interference measurement is
useful for MU-MIMO feedback as discussed above with regard to FIG.
8.
[0086] Accordingly, various embodiments of the present disclosure
provide that whether to perform subband based or full-band based
interference measurements may be configured by an eNB. For example,
such signaling may be higher layer configured or dynamically
signaled using a DCI format. When a UE is configured with
transmission mode (TM) 10 and is configured to perform full-band
based interference measurement, the UE derives the interference
measurements for computing each CQI value reported in uplink
subframe n and corresponding to a CSI process, based on only the
zero power CSI-RS (e.g., as defined in 36.211 v11.1.0) within the
configured CSI-IM resource associated with the CSI process, in the
DL system bandwidth (i.e., N.sub.RB.sup.DL). When a UE is
configured with TM 10 and is configured to perform subband-based
interference measurement, the UE derives the interference
measurements for computing each CQI value reported in uplink
subframe n and corresponding to a CSI process, based on only the
zero power CSI-RS (e.g., as defined in 36.211 v11.1.0) within the
configured CSI-IM resource associated with the CSI process, within
the subband(s) in which the CQI is derived.
[0087] Various embodiments of the present disclosure recognize that
time-domain aspects of the interference measurement include that,
for a UE in TM 10, the UE derives the interference measurements for
computing the CQI value reported in uplink subframe n and
corresponding to a CSI process, based on only the zero power CSI-RS
within the configured CSI-IM resource associated with the CSI
process. If the UE in transmission mode 10 is configured by higher
layers for CSI subframe sets C.sub.CSI,0 and C.sub.CSI,1, the
configured CSI-IM resource within the subframe subset belonging to
the CSI reference resource is used to derive the interference
measurement.
[0088] Various embodiments of the present disclosure recognize that
interference measurements may need to be performed in the
configured CSI-IM resource across multiple subframes corresponding
to the subframe subset. For example, interpolating multiple
interference measurements over time provides us reliable
interference measurement. On the other hand, if the UE is not
allowed to do timing interpolation for the interference reporting
(i.e., when the UE is instructed to measure interference within a
small set of subframes), eNB may allocate different interfering
signals for the UE across different time instances. By doing this,
the eNB may identify various CQI values calculated across different
interference hypotheses over time. This operation seems to be quite
beneficial for MU-MIMO scheduling.
[0089] Accordingly, various embodiments of the present disclosure
provide that whether to perform time-unrestricted or
time-restricted interference measurements may be configured by an
eNB. For example, such signaling may be higher layer configured or
dynamically signaled using a DCI format. When a UE is configured in
TM 10, the UE derives the interference measurements for computing
the CQI value reported in uplink subframe n and corresponding to a
CSI process, based on only the zero power CSI-RS (e.g., as defined
in 36.211 v11.1.0) within the configured CSI-IM resource associated
with the CSI process. If the UE in transmission mode 10 is
configured by higher layers for CSI subframe sets C.sub.CSI,0 and
C.sub.CSI,1, the configured CSI-IM resource within the subframe
subset belonging to the CSI reference resource is used to derive
the interference measurement. When the UE is configured to perform
time-restricted interference measurement, the UE measures
interference in designated subframes only. When the UE is
configured to perform time-unrestricted interference measurement,
the UE is allowed to measure interference without any subframe
restriction.
[0090] FIG. 12 illustrates subframe transmissions 1200 for
interference measurement in time-domain in accordance with various
embodiments of the present disclosure. The transmissions 1200
include two subframe subsets 1205 and 1210, CSI-IM resource
transmissions 1215, and CQI reporting in uplink subframe n 1220.
The UE is configured with two subframe subsets 1205 and 1210, and
the UE reports CQI in subframe n 1220, which is associated with
subframe subset 0 1205. The CQI reference resource is within
subframe n-n.sub.CQI.sub.--.sub.ref and belongs to subframe subset
0 1205. It is also noted that subframes n-3,
n-n.sub.CQI.sub.--.sub.ref, and n-n.sub.CQI.sub.--.sub.ref-2 belong
to subframe subset 0 1205, while the other subframes illustrated in
FIG. 12 belong to subframe subset 1 1210.
[0091] In another example, the designated subframes may correspond
to a single subframe, on which CSI reference resource is defined.
For example, the CSI reference resource may be defined according to
Section 7.2.3 of 36.213 v11.1.0. In FIG. 12, the designated
subframe according to this example is subframe
n-n.sub.CQI.sub.--.sub.ref.
[0092] In another example, the designated subframes correspond to
N.sub.IMR subframes, where N.sub.IMR is (Alt 1) a constant, or (Alt
2) configured in the higher layer (e.g., RRC). For computing the
CQI value in subframe n, the N.sub.IMR subframes are subframes
n-n.sub.CQI.sub.--.sub.ref-N.sub.IMR+1,
n-n.sub.CQI.sub.--.sub.ref-N.sub.IMR+2, . . . ,
n-n.sub.CQI.sub.--.sub.ref if subframe subsets are not configured.
If subframe subsets are configured, the N.sub.IMR subframes are
subframe n-n.sub.CQI.sub.--.sub.ref, and N.sub.IMR-1 more subframes
that precedes subframe n-n.sub.CQI.sub.--.sub.ref in the same
subframe subset belonging to the CSI reference resource. For
example, if N.sub.IMR=2 and UCI transmission is as illustrated in
FIG. 12, if subframe subsets are not configured, the designated
subframe according to this example is subframes
n-n.sub.CQI.sub.--.sub.ref and n-n.sub.CQI.sub.--.sub.ref-1. If
subframe subsets are configured, the designated subframe according
to this alternative is subframes n-n.sub.CQI.sub.--.sub.ref and
n-n.sub.CQI.sub.--.sub.ref-2.
[0093] In one exemplary embodiment, time-restricted and
frequency-restricted interference measurements may be jointly
configured by an eNB. Such signaling may be higher layer configured
or dynamically signaled using a DCI format, which may configure one
of the following two states: state 0: time-restricted and
frequency-restricted (or subband based) interference measurement,
and state 1: time-unrestricted and full-DL bandwidth interference
measurement.
[0094] In one embodiment, the present disclosure provides to
implicitly indicate the co-channel interference using CSI-IM
resources and for the UE to calculate MU-CQI taking into account
the interference measured in the CSI-IM resources.
[0095] In one embodiment, for example, as illustrated in FIG. 8, a
CSI feedback is based on a CSI process, and interference
measurements are restricted to the corresponding subband or
subbands in frequency. The `corresponding subband(s)` is the set of
subbands that the CQI feedback relates to in the feedback mode.
Furthermore, the interference measurement may be restricted in the
time domain as well as discussed above with regard to FIG. 12.
[0096] In one embodiment, whether to apply full-band or subband
interference measurement is configured by a higher layer (e.g.,
RRC) parameter. Each CSI process may convey the parameter. For
example, the interference measurement restriction may be
independently configured for different CSI processes. In one
example, the higher-layer parameter, Flag_Subband_CSI-IM
measurement, is included as part of the CSI process definition as
illustrated in Table 9 below.
TABLE-US-00009 TABLE 9 CSI-Process ::= SEQUENCE {
csi-ProcessIdentity-r11 CSI-ProcessIdentity-r11,
csi-RS-IdentityNZP-r11 CSI-RS-IdentityNZP-r11, csi-IM-Identity-r11
CSI-IM-Identity-r11, p-C-AndAntennaInfoDedList-r11 SEQUENCE (SIZE
(1..2)) OF P-C- AndAntennaInfoDed-r11, cqi-ReportBothPS-r11
CQI-ReportBothPS-r11 OPTIONAL, -- Need OR cqi-ReportPeriodicId-r11
INTEGER (0..maxCQI-Ext-r11) OPTIONAL, -- Need OR
cqi-ReportAperiodicPS-r11 CQI-ReportAperiodicPS-r11 OPTIONAL, --
Need OR Flag_Subband_CSI-IM measurement Boolean OPTIONAL, ... }
[0097] When Flag_Subband_CSI-IM measurement=1, the interference is
measured in the corresponding subband(s); when Flag_Subband_CSI-IM
measurement=0, the interference is measured in the full BW.
[0098] In one embodiment, whether to apply time-restricted or
time-unrestricted interference measurement is configured by a
higher layer (e.g., RRC) parameter. Each CSI process may convey the
parameter. For example, the interference measurement restriction
may be independently configured for different CSI processes. The
parameter is configured for each CSI process. In one example, the
higher-layer parameter, Flag_TimeRestricted_CSI-IM measurement, is
included as part of the CSI process definition as illustrated in
Table 10 below.
TABLE-US-00010 TABLE 10 CSI-Process ::= SEQUENCE {
csi-ProcessIdentity-r11 CSI-ProcessIdentity-r11,
csi-RS-IdentityNZP-r11 CSI-RS-IdentityNZP-r11, csi-IM-Identity-r11
CSI-IM-Identity-r11, p-C-AndAntennaInfoDedList-r11 SEQUENCE (SIZE
(1..2)) OF P-C- AndAntennaInfoDed-r11, cqi-ReportBothPS-r11
CQI-ReportBothPS-r11 OPTIONAL, -- Need OR cqi-ReportPeriodicId-r11
INTEGER (0..maxCQI-Ext-r11) OPTIONAL, -- Need OR
cqi-ReportAperiodicPS-r11 CQI-ReportAperiodicPS-r11 OPTIONAL, --
Need OR Flag_TimeRestricted_CSI-IM measurement Boolean OPTIONAL,
... }
[0099] When Flag_TimeRestricted_CSI-IM measurement=1, time
restriction is applied for the interference; when
Flag_TimeRestricted_CSI-IM measurement=0, time restriction is not
applied.
[0100] In one embodiment, whether to apply restricted or
unrestricted interference measurement is configured by a higher
layer (e.g., RRC) parameter. Each CSI process may convey the
parameter. For example, the interference measurement restriction
may be independently configured for different CSI processes. When
restricted interference measurement applies, the UE measures
interference in the restricted resource in both time and frequency
domain (i.e., interference is measured in the subband(s) in the
designated subframes). In one example, the higher-layer parameter,
Flag_Restricted_CSI-IM measurement, is included as part of the CSI
process definition as illustrated in Table 11 below.
TABLE-US-00011 TABLE 11 CSI-Process ::= SEQUENCE {
csi-ProcessIdentity-r11 CSI-ProcessIdentity-r11,
csi-RS-IdentityNZP-r11 CSI-RS-IdentityNZP-r11, csi-IM-Identity-r11
CSI-IM-Identity-r11, p-C-AndAntennaInfoDedList-r11 SEQUENCE (SIZE
(1..2)) OF P-C- AndAntennaInfoDed-r11, cqi-ReportBothPS-r11
CQI-ReportBothPS-r11 OPTIONAL, -- Need OR cqi-ReportPeriodicId-r11
INTEGER (0..maxCQI-Ext-r11) OPTIONAL, -- Need OR
cqi-ReportAperiodicPS-r11 CQI-ReportAperiodicPS-r11 OPTIONAL, --
Need OR Flag_Restricted_CSI-IM measurement Boolean OPTIONAL, ...
}
[0101] When Flag_Restricted_CSI-IM measurement=1, time restriction
is applied for the interference; when Flag_Restricted_CSI-IM
measurement=0, time restriction is not applied.
[0102] In another embodiment, whether to apply restricted or
non-restricted interference measurement is implicitly configured by
a feedback mode. In one example, the restriction applies only in
the time domain; and when the interference measurement is
restricted, the UE measures interference across the full DL
bandwidth in the designated subframes only. In another alternative,
the restriction applies only in the frequency domain; and when the
interference measurement is restricted, the UE measures
interference within the subband(s) without time restriction. In
another example, the restriction applies both in the time and
frequency domains, and when the restriction applies, the UE
measures interference within the subband(s) in the designated
subframes.
[0103] In another embodiment, among feedback modes supporting
subband CQI feedback (e.g., PUSCH mode 2-0, 2-2, 3-0, 3-1, and 3-2;
and PUCCH mode 2-0 and 2-1), restricted interference measurement
applies for a first set of feedback modes; and non-restricted
interference measurement applies for a second set of feedback
modes. For example, for feedback modes associated with UE-selected
subband CQI (e.g., PUSCH mode 2-0, 2-2; and PUCCH mode 2-0 and
2-1), the UE applies non-restricted interference measurement. On
the other hand, for feedback modes associated with higher-layer
configured CQI (i.e., PUSCH mode 3-0, 3-1, and 3-2), restricted
interference measurement applies. In another example, for feedback
modes associated with periodic CSI (i.e. PUCCH mode 2-0 and 2-1),
the UE applies non-restricted interference measurement. On the
other hand, for feedback modes associated with aperiodic CSI (i.e.,
PUSCH mode 2-20, 2-2, 3-0, 3-1, and 3-2), restricted interference
measurement applies.
[0104] In one embodiment, a UE is configured to report first and
second CSI reports. The UE is further configured to perform
restricted interference measurement for the first CSI feedback and
unrestricted interference measurement for the second CSI feedback.
In another embodiment, the restriction applies only in the time
domain. When the interference measurement is restricted, the UE
measures interference across the full DL bandwidth in the
designated subframes only. In another example, the restriction
applies only in the frequency domain. When the interference
measurement is restricted, the UE measures interference within the
subband(s) without time restriction. In another alternative, the
restriction applies both in the time and frequency domains. When
the restriction applies, the UE measures interference within the
subband(s) in the designated subframes.
[0105] In one example, the first CSI feedback reporting is
configured by a first CSI process configuration, and the second CSI
feedback reporting is configured by a second CSI process
configuration.
[0106] In another embodiment, for selected aperiodic CSI feedback
modes (e.g., for PUSCH based 3-2 aperiodic feedback mode), the UE
may be configured to feed back the first and second CSI reports
together. It may be difficult to justify PUSCH 3-2 feedback payload
without corresponding gains, so a second CSI feedback is for
MU-CQI. The eNB may obtain accurate CQI using any particular form
of precoding (e.g., ZF precoding), since the effect of precoding
may be reflected on CSI-IM resources. In this embodiment, in one
example, the two CSI reporting is implemented according to a single
joint CSI process as illustrated in Table 12 below. In this
example, an eNB may reflect co-channel interference on the CSI-IM
measurement.
TABLE-US-00012 TABLE 12 CSI-Process ::= SEQUENCE {
csi-ProcessIdentity-r11 CSI-ProcessIdentity-r11,
csi-RS-IdentityNZP-r11 CSI-RS-IdentityNZP-r11, csi-IM-Identity1-r11
CSI-IM-Identity-r11, csi-IM-Identity2-r11 CSI-IM-Identity-r11,
conditioned on PUSCH mode 3-2. p-C-AndAntennaInfoDedList-r11
SEQUENCE (SIZE (1..2)) OF P-C- AndAntennaInfoDed-r11,
cqi-ReportBothPS-r11 CQI-ReportBothPS-r11 OPTIONAL, -- Need OR
cqi-ReportPeriodicId-r11 INTEGER (0..maxCQI-Ext-r11) OPTIONAL, --
Need OR cqi-ReportAperiodicPS-r11 CQI-ReportAperiodicPS-r11
OPTIONAL, -- Need OR ... }
[0107] The CSI-Process configuration IE above includes a new field,
csi-IM-Identity2-r11, as well as csi-IM-Identityl-r11 for the
CSI-IM. csi-IM-Identity2-r11 may alternatively be configured in
aperiodic CSI reporting configuration (e.g.,
cqi-ReportAperiodicPS-r11 or equivalent) when configuring PUSCH
mode 3-2.
[0108] For periodic CSI reporting, the UE derives a single type of
CSI according to the periodic CSI configuration, based on the NZP
CSI-RS configuration (e.g., corresponding to
csi-RS-IdentityNZP-r11) and CSI-IM configl (e.g., corresponding to
csi-IM-Identityl-r11), where the interference is measured in the
full bandwidth according to CSI-IM config1. In one example,
csi-IM-Identity2-r11 may be configured only when the selected
aperiodic CSI feedback modes (e.g., PUSCH mode 3-2) are configured.
Even if csi-IM-Identity2-r11 is configured, the state of the
csi-IM-Identity2-r11 is not used for changing UE behaviors for
periodic CSI reporting.
[0109] When csi-IM-Identity2-r11 is configured, the aperiodic CSI
calculation reporting for the PUSCH reporting is according to the
following. The first CSI is calculated/reported based on the NZP
CSI-RS configuration (e.g., corresponding to
csi-RS-IdentityNZP-r11) and CSI-IM config1 (e.g., corresponding to
csi-IM-Identity1-r11), where the interference is measured without
resource restriction according to CSI-IM config1. Additionally, the
second CSI is suitable for MU and is calculated/reported based on
the NZP CSI-RS configuration and CSI-IM config2(e.g., corresponding
to csi-IM-Identity1-r12), where the interference is measured with
resource restriction according to CSI-IM config2.
[0110] On the PUSCH report, the first CSI comprises N.sub.sb pairs
(e.g., subband PMI, subband CQI), and the second CSI also comprises
N.sub.sb pairs (e.g., subband PMI, subband CQI), and the first and
the second CSI are jointly encoded.
[0111] The CQI estimation configuration for the two CSI reports is
illustrated in FIG. 5. CQI for the first CSI report is calculated
with interference measurement based on CSI-IM Config 1 505
configured by a CSI-IM configuration corresponding to
csi-IM-Identity1-r11; CQI for the first CSI report is calculated
with interference measurement based on CSI-IM Config 1 505
configured by a CSI-IM configuration corresponding to
csi-IM-Identity2-r11. In some examples, the UE may perform an
unrestricted interference measurement for the first CSI, and the UE
may perform a subband restricted interference measurement for the
second CSI.
[0112] In one example, the CQI calculation/reporting for the second
CSI report is a delta CQI to the CQI for the first CSI report. This
example may reduce CQI reporting overhead. In another example, CQI
calculation/reporting for the first and the second CSI reports are.
absolute (e.g., normal) CQI (i.e., no CQI compression is applied
for neither of the CQIs) for simplicity.
[0113] In one example, a single RI is reported for the CSI process,
where the single RI is calculated according to the first CSI, which
is for SU-CQI. For the second CSI, the RI is not reported. In
another example, the second CSI (i.e., PMI/CQI) is calculated
according to the RI for the first CSI. In another example, the
second CSI is calculated according to an implicit assumption that
the RI is equal to a constant (e.g., 1). In another example, two
separate RIs are calculated/reported for the first and the second
CSI for the CSI process.
[0114] Although the present disclosure has been described with an
exemplary embodiment, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present disclosure encompass such changes and modifications as fall
within the scope of the appended claims.
* * * * *